The present invention relates to power operated garage doors, and more specifically, to a power operated garage door of the type which may be installed in the wall of a house so that it is flush with the side wall of the house with an exposed outer surface of the door being of siding or masonry to blend in with the walls of the house providing a door which is essentially concealed from view.
Disclosed in my U.S. Pat. No. 5,341,597 issued on Aug. 30, 1994 on Power Operated Garage Door is a garage door adapted to be mounted with its exterior surface flush with the outside wall of a house so that the door may be made compatible with the side walls of the house and concealed from view. This type of door requires a mounting and an opening mechanism which are quite different from that found in the conventional domestic garage door in that, because of door's flush mounting, it must be shifted inwardly to clear the walls defining the door opening before it may be moved upwardly. The problem of mounting and raising the door is further complicated by the fact the door itself is much greater in weight due to the fact that door must be adapted to support a layer of masonry corresponding to the outer surface of the walls of the house. The door may in some instance weigh three or four times as much as a conventional garage door.
As disclosed in my above cited patent, the garage door is supported by two sets of tracks positioned on both sides of the garage door opening. One of the sets of tracks is disposed substantially vertical and receives guides mounted at the lower edge of the door and causes the lower edge of the door to move vertically as the door moves between the open and closed positions. The other set of tracks extends inwardly along the ceiling of the garage and receives guides mounted at the upper edge of the garage door so that, as the door opens, the door moves from a vertical door closed position to horizontal door open position in which the door extends inwardly from the door opening across the ceiling of the garage.
As compared to the common multipaneled doors, the door of the present invention and as disclosed in the above cited patent is a one piece door. Although there are one piece doors in widespread use in residential garages, such one piece doors are typically light in weight and are raised and lowered by mechanisms that would not be readily adaptable to handling the weight associated with doors constructed to blend with the exterior configuration of a house as contemplated by the present invention. In order to cope with the loads associated with this type of door, it is contemplated that door would be raised and lowered by flexible connectors such as cables or link chains which would be arranged to pull the door up to open and pull it down to close it. The advantages of this type of drive arrangement are discussed in my above cited patent. In general, however, the use of the flexible connectors to drive the door to the closed position rather than rely on gravity to close the door allows the use of safety mechanisms that respond to the load on the drive motor to sense obstructions to the movement of the door.
One of the problems associated with driving a one piece garage door of high mass by means of cables or other flexible connectors relates to the connection between the connector and the door. Because of the fact that the door moves between a vertical and a horizontal position and is displaced inwardly from flush with the house wall to a position adjacent the ceiling of the garage, it is almost required that the point of connection be located at the point where the lower edge of the door is guided in the vertical tracks. If the connection is made directly to the door, problems may result from the changing of the direction of force application through the flexible connector if the point of connection is not located on the horizontal axis about which the door pivots. As disclosed in my above cited issued patent, this connection may be made at the shaft which typically supports the guide rollers received in the guide tracks. The very large loads carried by the flexible connectors when lifting a masonry surfaced door present serious design problems in providing a strong enough roller support shaft. The roller support shaft is likely to deform under such loads and cause the mechanism to malfunction. Rather than increasing the size and strength of the support shaft, it would be desirable to use the standard light weight shaft for the door guides and apply the lifting force through the flexible cables directly to the door. There is, however, limited space between the edge of the door and the guide track. The connection must be made in this space if it is to be interior of the house wall and if the cable is not to interfere with the door as it moves between the vertical and horizontal positions.
In the prior art door as exemplified by my above cited patent, the cable connection to the door was made through the axle which pivotally mounted the lower guide rollers received in the vertical tracks provided to guide the lower edge of the door as it moved between the open and closed positions. The axles and the rollers were offset inwardly of the inner face of the door. While this arrangement is typical of the positioning of garage door guide rollers for the conventional multi-panel garage door, when this approach is applied to the much heavier and thicker masonry faced doors of the present invention, it results in the lifting force being applied to the door at a point offset horizontally from the vertical plane in which the center of gravity of the door is located. Because of this offset of the lifting force with respect to the center of gravity, a turning moment is created on the door which in turn increases the frictional forces in the guide tracks as the door moves upwardly. In the interests of reducing the forces necessary to raise and lower the heavy doors associated with the flush doors with which this invention is concerned, it is important to minimize any frictional forces generated in connection with guiding the door as it moves between its open and closed positions.
There is another problem relating to the location of the lower bearing about which the door pivots as it moves between the open and closed positions. While it is desirable to locate the horizontal axis of this bearing beneath the door or as close to the bottom edge as possible, it is also necessary to provide sufficient space in the vertical direction below this bearing for the pull down cable to extend down around a floor mounted pulley and then extend upwardly to the drive roller. Therefore, the cable connection to the door should be positioned toward the bottom of the door but should not interfere with the sealing of the door against the floor when it is in the closed position. This positioning of the bearing and the cable connection is further complicated by the fact that if the bearing is located upwardly from the bottom of the door, the pivoting of the door will cause the bottom of the door to extend into the door opening preventing the use of a sealing flange along the edge of the door to seal against the wall defining the door opening. From the foregoing, it is clear that the positioning and location of the lower door support bearing and the cable connection to the door is complicated by the path of movement of the door and the sealing requirements and the need to make the cable connection in the very limited space between the edge of the door and the adjacent wall defining the door opening. The only teaching in the prior art as to the considerations involved in the location of the bearing and the form of the cable connection is found in my prior U.S. Pat. No. 5,341,597.